Horton

Re: On disable_cost

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>, Peter Geoghegan <pg@bowt.ie>, David Rowley <dgrowleyml@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2024-07-02T19:36:56Z
Lists: pgsql-hackers 
Robert Haas <robertmhaas@gmail.com> writes:
> What the patch does is: if you set either enable_indexscan=false or
> enable_indexonlyscan=false, then the corresponding path type is not
> generated, and the other is unaffected. To me, that seems like the
> logical way to clean this up.

> One could argue for other things, of course. And maybe those other
> things are fine, if they're properly justified and documented.

[ shrug... ]  This isn't a hill that I'm prepared to die on.
But I see no good reason to change the very long-standing
behaviors of these GUCs.

			regards, tom lane

Commits

  1. Doc: add detail about EXPLAIN's "Disabled" property

  2. Adjust EXPLAIN's output for disabled nodes

  3. Fix order of parameters in a cost_sort call

  4. Show number of disabled nodes in EXPLAIN ANALYZE output.

  5. Treat number of disabled nodes in a path as a separate cost metric.

  6. Remove grotty use of disable_cost for TID scan plans.